They quite often rebury remains from more recent burials in the UK (100-200 years ago), for instance if the land of an old cemetery is repurposed (there have actually been several examples of this on HS2 as well). I don't quite know what the criteria is, but I think if there is little scientific value in the find, they will tend to rebury it. What will happen is they exhume the graves, categorise everything, and then rebury the remains.